For a variety of electronics, exposure to water is of concern due to water damage that can occur. For this reason, many companies are transitioning to product designs that are waterproof that offer oleophobicity and hydrophobicity. In doing so, such products also maintain clear acoustics for the microphones and speakers that are present in the device. Manufacturers would like to rate their products with a minimum of IPx7. This rating specifies that their products could survive being submerged to a depth of 1 meter for ½ hour without damage. A filter or vent is necessary for electronic devices to allow for pressure equalization, allowing the transducers to function properly.
Filters containing expanded polytetrafluoroethylene (ePTFE) are available to provide the necessary water protection for microphones and speakers. Acoustic vents are used to protect speakers and microphones from water and dust. Often these vents consist of expanded PTFE membranes. The PTFE membrane prevents water and/or dust from reaching the microphone or speaker, while also allowing the acoustic signal to pass through with minimal loss.
PTFE membranes are used because they can be manufactured to have low basis weight and high flexibility. These properties allow them to vibrate easily when excited by an acoustic signal, and transmit the acoustic signal to the other side without allowing liquid intrusion. In addition, PTFE membranes are gas permeable, allowing equalizations of differential pressures due to temperature changes, as well as the evacuation of moisture due to condensation. PTFE membrane also has high dust efficiency and can withstand high differential water pressure without any liquid water passing through.
Typically, such vents take the form of a disc being secured to the electronic housing covering a transducer. The industry has placed emphasis on achieving aesthetic goals such as filter color, while maintaining standards for acoustic performance, airflow and filtering ability. Additionally, conventional understanding dictates that an increase in basis weight and a decrease in flexibility of the PTFE membrane, such as through coating or laminating the PTFE, results in reduced acoustic performance of the vent. Such conventional understanding has been supported by transmission loss testing that has provided data demonstrating the decreased acoustic performance of such materials.